1. Field of the Invention
The present invention relates to a fluororubber composition, and, more specifically, relates to a fluororubber composition which is highly suitable for blending or processing on a roll mill and which is readily released from molds during a molding operation. With the optional addition of a specified silane the composition develops excellent adhesion to a variety of substrates during curing.
2. Description of the Prior Art
Organic fluorine containing rubbers, also referred to as fluororubbers, are used in a broad range of industrial applications due to their excellent mechanical properties. A shortcoming of these rubbers is the difficulty of fabricating them on roll mills and achieving a good release of the cured fluororubber from molds. In addition, the molds have a definite tendency to become soiled during molding operations, which together with the poor release properties results in a high reject rate.
The use of finely divided fluororubber particles as modifiers for a polyorganosiloxane elastomer is disclosed in Japanese unexamined published application no. 60/105,557, which issued on June 11, 1985. Japanese unexamined published application No. 60/112,431, which was published on June 18, 1985, teaches using these modified fluororubber compositions as the material for preparing thermal fixing rolls for electrostatic copying machines.
U.S. Pat. No. 4,488,771, which issued on Dec. 18, 1984, describes molding compositions comprising a matrix of a fluorosilicone elastomer and a crosslinking agent containing dispersed particles of a solid fluorocarbon telomer.
U.S. Pat. No. 4,010,136, which issued on Mar. 1, 1977 discloses polyorganosiloxane elastomer compositions containing a silica filler an organic peroxide and powdered polytetrafluoroethylene as a dispersed phase.
In all of the aforementioned prior art the continuous phase is a polyorganosiloxane and the dispersed phase is a fluorocarbon polymer.
The present invention was the result of extensive investigations directed at solving the aforementioned problems with fluororubbers.
The object of the present invention is to provide a curable fluororubber composition which is excellent with respect to (1) its ability to be fabricated on roll mills and the low reject rate of articles molded from these compositions, and (2) the excellent adhesion developed during curing between the rubber and a variety of substrates.
The present invention also provides a method for improving the processability of curable fluororubber compositions, specifically the ability of these compositions to be molded and fabricated using roll mills typically used for other types of rubber compositions. This invention also provides additives for improving the adhesion of the cured fluororubber compositions to metal and plastic substrates.